As with most other joints in the body, the SI joints have a cartilage layer covering the bone, which allows for some movement and acts as a cushion between the bones. When this cartilage is damaged or worn down, the bones begin to rub on each other. This is the most common cause of a condition called SI Joint Dysfunction.
There are many different terms for sacroiliac (SI) joint dysfunction, including sacroiliac joint disorder, sacroiliac joint syndrome, sacroiliac joint strain and sacroiliac joint inflammation. Each of these terms refers to a condition that causes pain in the sacroiliac joints and results in lower back pain and/or leg pain.